

THE CHEMISTRY OF BACTERIA. 105 



pointed out (p. 28) that the cell- wall of many bacteria may 

 soften or gelatinize, giving- rise to the so-called capsule. 

 The organisms, in such cases, tend to stick together, form- 

 ing' zoogleae. 



Several of these fermentations are of interest, because 

 the gummy substance which is produced, known as visa 

 or dextran, is a carbohydrate allied to dextrin. Its formula, 

 C 6 H 10 O 5 is the same as that of dextrin. Among- the by-pro- 

 ducts in this case may be mentioned carbonic and lactic 

 acids, and mannite. The latter probably, results by the ac- 

 tion of nascent hydrogen on glucose. The Leuconostoc mes- 

 enterioides is a common cause of such fermentations in molas- 

 ses, etc., in sugar refineries. This organism, when grown 

 in sugar solutions, develops enormous capsules, which are 

 10 or 20 times the width of the cell itself. On the usual 

 nutrient media it appears as an ordinary streptococcus. 

 Under favorable conditions it may develop with extreme 

 rapidity, converting the sugar solution into a jelly, or even 

 into a cartilaginous mass. In one instance, 80 barrels of 

 molasses became converted into a gelatinous mass within 

 12 hours A temperature .of 30-35 favors this fermentation. 



Fermentation of fats. The various animal and vegetable 

 fats or oils are essentially neutral compounds of glycerin 

 and one or more fatty acids. A strictly pure fat cannot be 

 acted upon by bacteria, inasmuch as it contains only C, H 

 and O. It may, however, become rancid by exposure to the 

 action of air and light. The change that results consists 

 in the splitting of the fat into its components, glycerin and 

 fatty acids. If, on the other hand, the fat is not pure but 

 contains nitrogenous and other matter it will be possible 

 for bacteria to grow in .such a mass. In that event, a more 

 or less extensive fermentation, or cleavage of the fat will 

 occur. 



The decomposition of fat by means of bacteria is a 

 constant occurrence in the intestines. The change which 



